u-boot/arch/arm/cpu/arm1136/mx35/timer.c

/*
 * (C) Copyright 2007
 * Sascha Hauer, Pengutronix
 *
 * (C) Copyright 2008-2009 Freescale Semiconductor, Inc.
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

#include <common.h>
#include <asm/io.h>
#include <div64.h>
#include <asm/arch/imx-regs.h>
#include <asm/arch/crm_regs.h>
#include <asm/arch/clock.h>

DECLARE_GLOBAL_DATA_PTR;

#define timestamp	(gd->arch.tbl)
#define lastinc		(gd->arch.lastinc)

/* General purpose timers bitfields */
#define GPTCR_SWR       (1<<15)	/* Software reset */
#define GPTCR_FRR       (1<<9)	/* Freerun / restart */
#define GPTCR_CLKSOURCE_32   (4<<6)	/* Clock source */
#define GPTCR_TEN       (1)	/* Timer enable */

/*
 * "time" is measured in 1 / CONFIG_SYS_HZ seconds,
 * "tick" is internal timer period
 */
/* ~0.4% error - measured with stop-watch on 100s boot-delay */
static inline unsigned long long tick_to_time(unsigned long long tick)
{
	tick *= CONFIG_SYS_HZ;
	do_div(tick, MXC_CLK32);

	return tick;
}

static inline unsigned long long us_to_tick(unsigned long long us)
{
	us = us * MXC_CLK32 + 999999;
	do_div(us, 1000000);

	return us;
}

/*
 * nothing really to do with interrupts, just starts up a counter.
 * The 32KHz 32-bit timer overruns in 134217 seconds
 */
int timer_init(void)
{
	int i;
	struct gpt_regs *gpt = (struct gpt_regs *)GPT1_BASE_ADDR;
	struct ccm_regs *ccm = (struct ccm_regs *)CCM_BASE_ADDR;

	/* setup GP Timer 1 */
	writel(GPTCR_SWR, &gpt->ctrl);

	writel(readl(&ccm->cgr1) | 3 << MXC_CCM_CGR1_GPT_OFFSET, &ccm->cgr1);

	for (i = 0; i < 100; i++)
		writel(0, &gpt->ctrl); /* We have no udelay by now */
	writel(0, &gpt->pre); /* prescaler = 1 */
	/* Freerun Mode, 32KHz input */
	writel(readl(&gpt->ctrl) | GPTCR_CLKSOURCE_32 | GPTCR_FRR,
			&gpt->ctrl);
	writel(readl(&gpt->ctrl) | GPTCR_TEN, &gpt->ctrl);

	return 0;
}

unsigned long long get_ticks(void)
{
	struct gpt_regs *gpt = (struct gpt_regs *)GPT1_BASE_ADDR;
	ulong now = readl(&gpt->counter); /* current tick value */

	if (now >= lastinc) {
		/*
		 * normal mode (non roll)
		 * move stamp forward with absolut diff ticks
		 */
		timestamp += (now - lastinc);
	} else {
		/* we have rollover of incrementer */
		timestamp += (0xFFFFFFFF - lastinc) + now;
	}
	lastinc = now;
	return timestamp;
}

ulong get_timer_masked(void)
{
	/*
	 * get_ticks() returns a long long (64 bit), it wraps in
	 * 2^64 / MXC_CLK32 = 2^64 / 2^15 = 2^49 ~ 5 * 10^14 (s) ~
	 * 5 * 10^9 days... and get_ticks() * CONFIG_SYS_HZ wraps in
	 * 5 * 10^6 days - long enough.
	 */
	return tick_to_time(get_ticks());
}

ulong get_timer(ulong base)
{
	return get_timer_masked() - base;
}

/* delay x useconds AND preserve advance timstamp value */
void __udelay(unsigned long usec)
{
	unsigned long long tmp;
	ulong tmo;

	tmo = us_to_tick(usec);
	tmp = get_ticks() + tmo;	/* get current timestamp */

	while (get_ticks() < tmp)	/* loop till event */
		 /*NOP*/;
}

/*
 * This function is derived from PowerPC code (timebase clock frequency).
 * On ARM it returns the number of timer ticks per second.
 */
ulong get_tbclk(void)
{
	return MXC_CLK32;
}